Russia-related investments were a key issue in a televised debate among candidates for the U.S. state of Montana's seat in the House of Representatives.

Democrat Rob Quist on April 29 criticized his Republican rival, Greg Gianforte, for holding some $240,000 in investments that disclosures link to funds with holdings in Russian companies hit by U.S. sanctions.

The sanctions were imposed under the Obama administration because of Russia's illegal annexation of Ukraine's Crimea Peninsula.

The candidates are running in a special election on May 25 for Montana's only House seat. It became vacant in March when Ryan Zinke resigned to become U.S. Secretary of the Interior.

"I was really dispirited to hear the other day that Mr. Gianforte has a quarter of a million dollars in stocks in Russian companies that are on the sanctions list," Quist said.

Gianforte defended his investments.

"Anyone who invests in emerging markets around the world has investment in Russia," Gianforte said, calling it a small portion of his investments.

His campaign has acknowledged $150,000 in investments with VanEck Vectors Russian and $92,000 with IShares MSCF Russia. Both companies deal in exchange-traded funds, which are similar to mutual funds.

Gianforte made millions when he sold his software firm, RightNow Technolgoies, to Oracle.

According to required disclosures, his total assets are in the range of $96 million to $327 million.